Drafting machine



Aug. 18, 1936. v. B. WALLACE 2,051,115

DRAFTING MACHINE Filed Jan. 8, 1954 2 Sheets-Sheet 1 .lllornfys Aug. 18,1936.

v. B. WALLACE DRAFTING MACHINE Filed Jan. 8, 1934 l IH 2 Sheet-Sheet 2Allllllll Patented ug. i8, 1936 DRAFTING MANE Vard B. Wallace, Alhambra,Calif.

Application .ianuary 8, 1931i, Serial No. 705,725

2 Claims. (Cl. Sii-'wl My invention relates to drafting machines and.has particular reference to machines for supporting scales or straightedges upon a drawing board so that the same may be moved to variousposi- 5 tions upon the board without changing the alignment of thescales or straight edges with predetermined base lines upon the board.

In the art of mechanical drafting, it is common practice to employ adrawing board upon which the paper of which the drawing is to .be

made is secured and to proceed with the construction of the drawing bydetermining a. base line on the drawing relative to which other linesare extended in parallel or at right angles thereto.

In making such drawings, particularly drawings of considerable size, itis difficult to maintain correct parallelism by the use of an ordinaryT- square and drafting machines of the type employing a jointed armsecured to the board and carrying scales or straight edges have beenemployed with the arm to insure maintenance of the straight edgesparallel to the predetermined base line independent of the movement ofthe arm to place the straight edges over various portions of the drawingboard.

An object of my invention is to provide a drafting machine of thischaracter, in which the scales or straight edges may be supported upona'single arm having a joint therein, and in which a flexible endlessbelt is employed to maintain the scales in alignment with apredetermined base line independent of movement of the arms.

Another object of the invention is to provide a drafting machine of thecharacter set forth in which an endless belt operating over pulleys isemployed to maintain alignment of the scales with a predetermined baseline independent of the movement of the arm, even though such arm lmaybe moved through several complete rotations.

Another object of the invention is to provide an arm construction for adrafting machine, as set forth, in which the arm may be readily adiustedto maintain taut relation with the endless band or bands.

Other objects and advantages of the invention will be apparent from astudy of the following specifications, read in connection with the waccompanying drawings, wherein Figure 1 is a plan view of a draftingmachine constructed in accordance with' my invention, attached to adrawing board; v

Figures 2 and 2a together are detail sectional views through one of thearm sections shown in Fig. i, the view being taken along line II-H ofFig. l;

Figure 3 is a detail plan view of the protractor and scale mountingemployed with my invention;

Figure t is a detail sectional view, taken along 5 line IV-IV of Fig. 3;

Figure 5 is a detail sectional view, taken along line V--V of Figure 3;

Figure 6 is a detail plan view illustrating a lock and latch which maybe employed with the l0 protractor constructed in accordance with myinvention; and

Figure 'l is a detail sectional view, taken along line Vil-VII of Fig.3, illustrating the hinged connection for the latch-operating mechanism.i6

R',ferring to the drawings, I have illustrated in F g. 1 a drawing boardI to whichV my drafting maci ine, illustrated at 2, maybe secured, as bymeant` of a clamp 3. The clamp 3 may be either permanently secured tothe board, as by screws, 20 or by suitable screw-clamping means, notshown, such as is commonly employed for the attachment of universaldrafting machines to drawing boards of the character herein set forth.

A pair of scales or straight edges t and 5 are 25 illustrated as beingcarried upon the outer end of a jointed arm, consisting of two sections6 and 1, a section of the arm 6 being formed with the bifurcated head Bapivotally secured upon a vertically extending shaft 8 rigidly connectedto 30 the clamp 3. The bifurcated head 6a preferably includes twobearing members 6b and 6c, having aligned openings therein for thereception of ball bearings 6d and 6e, respectively, so that the arm 6may be moved about the shaft 8 with relatively 35 little friction.

The shaft is illustrated as including a reduced section 8a, the end ofwhich is threaded as at 8b to receive a locknut 8c to securely hold thesame rigidly to the bracket 3, a suitable lock e0 washer 8d beinginterposed between the outer surface of the bracket 3 and a shoulder 8eformed upon the shaft 8. The upper portion of the shaft 8 is illustratedas being tapered as at 8f for reception in a tapered hub of a pulley 9,which pulley i5 may be clamped upon the shaft 8 as by means of a locknut9a, while the extreme upper edge 8g of the shaft 8 forms a bearingsurface for engaging the ball bearing 6d.

The major portion of the arm 6 is illustrated 50 as being formed of anelongated tube having a central bore 6j thereby permitting the same tobe relatively light, to which the head 6a may be attached as by means ofa plug 6g insertable in the bore Bf to extend beyond the outer end ofthe arm 6 anciA into a bore 6h in the head 6a where it may be attachedas by means of a pair of screws 6k and 6m. The screws 6k and 6m arepreferably threaded into the same threaded opening En so that byloosening one of the screws and tightening the other, the plug 6g may bealigned accurately in the center of the bore 6h. If desired, a suitablebearing collar 6p may be employed between the outer end of the head 6aand the end of the tubular arm 6.

Th-e inner end of the arm 8 is formed with a jointed head I0, to whichis fixed a shaft as by means of pressing the same through a ball bearingI a, and then pressing the ball bearing f into a suitable annular recess|0b formed in the ally mounted upon the shaft so that it is free to turnthereon, the pulley |2 being provided with a pair of grooves |3 and |4for the reception of a pair of bands I5 and I6. The band I5 isillustrated as extending from the pulley I2 to the pulley 9 and is,preferably, formed of a continuous strip of substantially non-stretchingmaterial, such as a thin ribbon of steel, which, when in taut relationon the pulleys I2 and 9, constitutes a traction device preventing anyrotational movement of one of the pulleys without causing acorresponding rotational movement of the other of the pulleys. Thus thepulley 9, being fixed upon the shaft 8, any movement of the arm 6 aboutthe shaft 8 will be accompanied by rotation of the pulley I2 about itsshaft exactly equal to the angle through which the arm 6 has beenrotated relative to the shaft 8. Thus any diameter of the pulley I2,relative to a corresponding diameter of the pulley 9, will always bemaintained in parallel relation independent of movement of the arm 6.

To permit ready adjustment of the band 5 and to permit the band to beremoved and replaced readily, the joint head I0 on the arm 6 is mountedupon the arm 6 for telescopic relation relative to the arm so that theeffective length of the arm-that is the distance between the centers ofthe pulley 8 and the pulley |2,- may be extended or contracted by suchtelescopic movement. This may be readily accomplished by providing aboss or plug Inlc on the head I0 to extend snugly into the bore Bf ofthe tubular arm 6 and providing in such plug a threaded bolt |0d, thehead IIIe of which is; provided with a slot engaged by an extendingtongue IIJf on a block IOg rigidly secured in the bore of the arm 6 asby forming such block with a knurled outer Y surface and forcing thesame in tight frictional engagement with the interior of the bore 6f.Thus by rotating the tubular arm 6, the bolt Id is screwed into or outof the block II'Ic, lengthening or shortening the distance between thecenters of the pulleys 9 and I2.

At this point it should be observed that the single arm 6 constitutes arigid support extending between the pulleys 9 and I2, which may beeffectively lengthened or shortened to maintain taut relation betweenthe pulleys and the band I5.

1a by a plug and bolt connection, corresponding to the plug |0c and bolt|0d, so that rotation of the tubular arm section 1 will also effectivelylengthen or shorten this arm.

Upon the outer end of the arm 1 is a scale supporting head I1, theconnection between the head I1 and the arm 1 being preferably identicalwith the connection between the arm section 6 and its head 6a. The headI1 is provided with a suitable bearing |1a pressed into a cylindricalopening I1b formed thereinto constitute a bearing upon which aprotractor and scale supporting structure may be rotatably mounted.'I'he protractor and scale supporting structure preferably includes apulley I8 secured to a disk I9 which is in turn rigidly secured to asleeve constituting a pivotal bearing engaging the ball bearing |1a heldin assembled relation upon the head I1 by means of a suitable washer 2|and a locknut 22 threaded upon the upper end of the sleeve 20. Thus theflexible band I6 extending between the pulley I2 and the pulley I8constitutes an interconnection of these pulleys similar to that formedby the band I5 between the pulleys 8 and I2, so that irrespective ofrotational movement of the arm'1, relative to the shaft correspondingvparallel diameters of the pulleys I2 and I8 will always remain parallel.

Thus the scales or straight edges 4 and 5 may be secured to the pulleyI8, irrespective of movement of the arms 6 and 1 over the board I, thesescales or straight edges 5 being once aligned with a base line willalways extend parallel to such base line, independent cf movement of thearm sections 6 and 1 over the board.

However, it is desirable that the scales or straight edges 5 should becapable of adjustment to angular positions relative to a given base lineon the board I and for this purpose I have provided means for adjustingthe scales 4 and 5 relative to the pulley I8 to permit the connectionbetween the pulley and the scales to constitute a protractor. This maybe readily accomplished by mounting the scales 4 and 5 upon an angularbracket 23 so that the scale 5 extends substantially parallel to thelower edge of the board I, while the scale 4 extends at right anglesthereto.

'I'he bracket 23 may be secured to a plate 24 as by means of a pair ofscrews 25 and 26, the screw 26 being provided with a suitable handle 21which permits ready loosening and tightening thereof so that byproviding a slot 28 in the bracket 23 the relative angular position ofthe scales and the plate 24 may be readily adjusted; for example, if adrawing previously made is placed upon the board with its base lines notin accurate parallelism with the edges of the board, these scales may beadjusted through the medium. of the screws 25 and 26 to parallel themwith the base lines of such drawing without disturbing the angularposition between the plate 24 and the pulley I8.

The plate 24 is illustrated as being secured as by means of rivets 29 toa base plate 30 which is rigidly mounted upon a shaft 3| extendingthrough the sleeve 20. The connection between the plate 38 and the shaft3| is preferably made by squaring off one end of the shaft 3|, asindicated at 32, and riveting the same to a spring plate 33 which is inturn secured as by means of screws 34 to the base plate 30. The shaft 3|being rotatably mounted in the sleeve 20, permits rotation of the baseplate with its scale bracket 23 relative to the pulley |8, so that byproviding a graduated scale plate 35 interposed between the disc I9 andthe pulley I 8, and providing a vernier plate 36 upon the plate 24, thescale plate 35 and the Vernier plate 36 having graduations 31 thereoncorresponding to degrees of rotation, the relative positions of the baseplate 38 and the pulley I8 may be set at any desired angle. For example,I have illustrated the scale plate 35 as having a zero calibration uponthe vernier plate 36 so that by shifting the base plate 38, relative tothe pulley, the zero calibration on the Vernier plate 36 may be alignedwith any of the other calibrations on the scale plate 35 to conform withthe angle desired between the straight edges 4 and 5 and the originalbase line upon which such scales may be set. f

However, in order to prevent accidental displacement of the base plate30, relative to the pulley I8, and to provide for ready adjustment ofthe plate and pulley to commonly employed angles, such as 30, 45, 60 and90, a plurality of holes 38 may be provided in the disk |9 to receivetherein a pin 39 projecting from the spring plate 33. Thus when the zerocalibration of the scale plate 35 and the vernier plate 36 are inalignment, the pin 39 will be received in one of the holes 38 to latchthe base plate 38 and the pulley in this relation.

A suitable handle 48 may be mounted upon the upper end of the shaft 3|to permit relative rotation of the base plate 38 and the pulley I8 whenthe pin 39 is withdrawn and it is desired to move the base plate 38 to anew angular position, the handle 48 being preferably secured to a disk4| which is received upon the upper end of the shaft 3| as by flatteningthe sides of the upper end of the shaft 3| so as to prevent relativerotation between the handle and the shaft.

rlo permit ready removal of the pin 39 from any one of the holes 38, Iprovide a finger-piece 42 pivotally mounted, as upon a shaft 43, setinto a recess 44 and held therein by the plate 24, the finger-piece 42being provided with a cam projection 45 such that when the finger-pieceis `ro tated about its pivot 43 it will engage the upper surface of theplate 33 and depress the same to remove the pins 39 from the holes 38.With the spring plate 33 in this position, the base plate 38 and pulleyI8 may be readily adjusted. However, if it is desired to lock thelatching devices 39 and 38 out of effective engagement with each other,a lock may be provided, consisting of a locking plate 46 pivoted to thebase plate 38, as at 41, and movable relative to the end of-the springplate 33, as by means of a finger-piece 48 extending through anelongated slot 49 in the plate 24 so that after the spring plate 33 hasbeen depressed the locking plate 46 may be moved over the outer end ofthe same to prevent the pin 39 from reengaging any of the holes 38.

With the latch 39-38 in this position, it may be desired to fix theangular positions of the base plate 38 and the pulley I8, and this maybe readily accomplished by means of a clamping screw 58 extendingthrough the base plate 38 and having a washer 5| thereon to becompressed into clamping relation upon the disc I9 by means of a nut 52.

It will therefore be observed that I have provided a drafting machine inwhich the scales are supported upon a protractor construction permittingthem to be readily adjusted to any angular positions relative to a zeroor base line, while, without disturbing the correct angular positions ofthe protractor mechanism, the scales may be adjusted independent thereofto a predetermined base line, already appearing upon a drawing.

It will also be observed that by employing the l single rigid armsection extending between the pulleys, and by employing the flexiblebands, the correct alignment of the scales with the base line will bemaintained independent of the movement of the arm sections over variousportions of the drawing board. Also, by employing the continuousflexible bands as the traction means between the pulleys, it is possibleto move the arm sections over all parts of the drawing board and, infact, to rotate the same completely around the shaft 8 withoutinterfering in any manner with the correct operation of the machine andwithout changing the true parallel relation of the scales with thepredetermined base line upon which they may be set.

It will also be observed that by permitting complete rotation of thesupporting arm sections about the shaft 8, it is possible for the scalesupporting structure and protractor to be adapted for use either by aright-handed or a left-handed draftsman, and also permits the protractorto be supported upon any part of the drawing board, its connection tothe bottom edge of the drawing board, rather than the top of the drawingboard, or to either of the side edges of the board, being equallypossible with my construction.

While I have shown and described the preferred embodiment of myinvention, I do not wish to be limited to any of the details shownherein, except as defined in the appended claims.

I claim:

1. In a drafting machine, means attachable to a drafting board, an armformed of a single tubular member having a pair of heads thereon atopposite ends thereof, pivot means mounting one of said heads to saidattaching means for movement in a plane parallel to the surface of -saidboard, a pulley fixed to said pivot means, a second pulley rotatablymounted on the other of.

said heads for rotation in a plane parallel to the surface of saidboard, a continuous flexible band interconnecting said pulleys, andmeans threadedly engaging one of said heads in said tubular member forvarying the distance between the centers of said pulleys to tighten orloosen said band.

2. In a drafting machine, means attachable to a drafting board, a pivoton said attaching means extending at right angles to the surface of saidboard, a pulley xed on said pivot means and extending in a planeparallel to the surface of said board, an arm comprising a singletubular member, a head on one end of said arm pivoted to said pivotmeans and having a stem extending into said tubular member in adirection at right angles to said pivot means, a second head threadedlysecured in the opposite end of said tubular member, whereby rotation ofsaid tubular member relative to said heads increases or decreases theeifective length of said arm, a second pulley pivoted to said secondhead for rotation in a plane parallel with the surface of said board,and a continuous iiexible band interconnecting said two pulleys.

VARD B. WALLACE.

